Bright, piquant boquerones, the vinegar-cured white anchovies of Spain, have a meatier texture than canned varieties.
Bring a large pot of salted water to a boil, and cook pasta until al dente, about 9 minutes. Drain, reserving 1/4 cup pasta water.
Heat 2 tablespoons oil in a large skillet over medium heat. Add breadcrumbs, and cook, stirring frequently, until golden brown, about 5 minutes. Drain on paper towels, and wipe out pan.
Heat 3 tablespoons oil in pan over medium-high heat. Add peppers and 1/2 teaspoon salt, and saute, stirring frequently, until peppers begin to soften, about 10 minutes, adjusting heat if they begin to brown. Transfer peppers to a plate, and add remaining oil to pan. Add garlic, and cook, stirring, until fragrant and lightly golden, about 2 minutes. Return peppers to pan, and add reserved pasta water; stir in capers. Toss well with pasta and parsley in a serving bowl. Add boquerones, and gently toss to combine. Season with pepper and, if necessary, salt. Top with breadcrumbs.